Abstract: Methods and apparatus for analyzing the material properties and behavior of cement as it hydrates under simulated downhole conditions are disclosed. A wellbore cement simulator includes a temperature and pressure controlled innermost oil-filled container; an annulus in contact with the innermost container configured to hold a cement sample; a mesh sleeve in contact with the annulus wherein the mesh sleeve is water permeable to permit hydration of the cement sample; a steel sleeve in contact with the mesh sleeve; an elastomeric bladder surrounding the steel sleeve; and a temperature and pressure controlled outermost oil-filled container.